During an airport ground rolling phase, the pilot of an aircraft generally receives an authorization from the control tower to follow a route around the traffic lanes of the airport. He uses airport maps which are printed on paper or which are displayed on a viewing screen of head-down type, to get his bearings and correctly follow the authorization given by the controller. For this purpose, the pilot compares his position with respect to the map with the aid of panels situated on the verges of the traffic lanes. The pilot is also responsible, during the rolling phases, for discharging an anti-collision function, that is to say for avoiding a collision with any craft, mobile or not, situated on a traffic lane, thus implying that he is permanently aware of the environment outside the aircraft. He must of course also ensure that the wheels of the aircraft do not leave the pavement of the traffic lane followed.
There are devices for aiding airport ground navigation which comprise a display system of head-up or HUD (“Head-Up Display”) type and which provide indications as regards the position of the wheels, the trajectory to be followed and the instruction to be applied in order to avoid leaving the traffic lanes, while following the authorization given by the controller.
A method and a device for aiding the ground navigation of an aircraft on an airport is known from document FR-2 901 903.
Depending on the complexity of the airport and the meteorological conditions, the pilot's task may be made more complicated and give rise to errors which lead to non-compliance with the authorization given by the controller. By way of example, heavy fog makes it difficult or indeed impossible to read the panels on the verge of the traffic lanes. This may lead to erroneous knowledge of the position on the traffic lanes and therefore to a wrong path being taken at the next intersection. The rolling authorization is then no longer complied with. Such a situation can become very dangerous when this error results in entry to a runway (landing or takeoff) without having received prior authorization.
Another problem which exists during such a rolling phase is that the pilot is responsible for discharging an anti-collision function, thus implying that his gaze is fixed outside. Such a situation is incompatible with the reading of the map (on paper or on a head-down screen) of the airport so as, for example, to ascertain the names of the traffic lanes at the next intersection and the direction to be taken.
Additionally, the use of a device for aiding airport navigation, such as aforementioned, in general requires that this device know the track along which the controller authorizes the aircraft to roll. As most ground rolling authorizations are provided with the aid of a radiocommunication, the pilot must enter this information manually into the device. This task can be laborious when the authorization is long and complicated. Moreover, if the authorization is modified during rolling, it is necessary to enter the new authorization while rolling, this being prejudicial to safety.
Furthermore, the use of a usual device such as this, in the rolling phases, demands great attention from the pilot in order to monitor the symbols displayed, this being done to the detriment of the knowledge of the outside situation.